Crossover sign after rotational acetabular osteotomy for dysplasia of the hip.

Background: This study was performed to evaluate whether the radiographic crossover sign influences the painful femoroacetabular impingement or the radiographic progression of osteoarthritis after rotational acetabular osteotomy (RAO).
Methods: A total of 104 patients (115 hips) with preosteoarthritis (pre-OA) or early-stage OA of the hip due to dysplasia underwent RAO. Their mean age at the time of surgery was 34.7 years. The mean follow-up period was 13 years. Clinical follow-up was performed with the system of Merle d'Aubigne, and the impingement sign was evaluated. Radiographic analyses included the center-edge angle, acetabular roof angle, head lateralization index (HLI), joint congruency, crossover sign, posterior wall sign, acetabular index of depth to width, pistol grip deformity, and femoral head/femoral neck ratio.
Results: The mean clinical score improved significantly from 14.6 preoperatively to 17.0 at follow-up. The impingement sign at follow-up was observed in 14 hips (12.2%). The center-edge angle, acetabular roof angle, and head lateralization index (HLI) improved significantly after surgery. The crossover sign was observed in 8 hips (7.0%) preoperatively and in 49 hips (42.6%) postoperatively. The posterior wall sign was observed in 70 hips (60.9%) preoperatively and in 73 hips (63.5%) postoperatively. The impingement sign after RAO was positive significantly in the postoperative crossover sign-positive hips. Radiographic progression of OA was observed in 11 hips (crossover sign was positive in 7 hips and negative in 4 hips). The only factors significantly associated with radiographic progression after RAO were fair postoperative joint congruency and age at surgery.
Conclusions: Although there was no significant radiographic progression of OA despite significant retroversion, anterior impingement and radiographic crossover sign after RAO are should be checked during the procedure. The goal of RAO should be correct alignment of the acetabulum including a correct version with a negative crossover sign.